Interesting - I was trying to figure out how this would be possible, and it would indeed depend on a coil producing both positive and negative high voltages. There's no other way to do it. I still don't see how it could be a series circuit the way you described it. There's no incentive for the electrons to travel past the block. They're satisfied at that point.

Arthur Dalton - I think you might have it slightly backwards. In other words, I don't think the spark travels across the block to another plug. There's no electrical incentive for them to do that. They're at ground potential at that point and it makes 'em lazy. Here's what I think is happening, using 10KV for easy math....

1) Compressed cylinder gets +10KV to center electrode. This draws electrons from the block to the center electrode
2) Those electrons have now traveled to the coil on the positively charged spark plug wire, where they become available to go out the negative end of the coil, or not.
3) The electrons travel out the negative end of the coil to the waste spark cylinder's center electrode. Because they are more negative than ground, they travel from the center electrode to the rim, where they meet ground. Circuit complete.

The reason I said "or not" in step two is because in this setup, it would not be necessary for both plugs to work in order to get one to spark, though it might make a difference in spark intensity if one were not. If the coil is producing high voltage in both positive and negative, either form of spark would be satisfied by the ground potential of the battery/chassis.

I think the reason you've got it backwards is because you're not quite correct about polarity. Electrons flow from the negative towards the positive. Therefore, a high positive voltage applied to the center electrode will cause a spark to jump from the edge electrode towards center. The opposite is also true.

Also, I think the "series" part of this circuit is in the coil, not the plugs. The two high voltage + and - taps are inherently in series........

Either way, I don't see high voltage traveling across the block and then across another air gap. Not gonna happen.


-tp